The present invention is generally related to a backlight module, and more particularly, to a light source, a fluorescent lamp and a backlight module utilizing the same.
Currently, the main light source of a conventional backlight module is cold cathode fluorescent lamps (CCFLs). As shown in FIG. 1A, a conventional CCFL 10′ comprises a hollow glass tube 11′, electrodes 12a′ and 12b′, and wires 13a′ and 13b′. The electrodes 12a′ and 12b′ and the wires 13a′ and 13b′ are disposed at each end of the hollow glass tube 11′, respectively. The hollow glass tube 11′ contains mercury (Hg), phosphor, and inert gas (not shown). The electrodes 12a′ and 12b′ are cylindrical and made of metal. When a high voltage is applied to the electrode 12a′ of the hollow glass tube, electrons are emitted from the electrode 12b′ at low voltage end to the electrode 12a′ at high voltage end. The electrons are accelerated due to the high voltage, causing collisions with the Hg atoms in the hollow glass tube 11′. After collision with the Hg atoms, the Hg atoms quickly return to their stable state, and excess energy produces ultraviolet (UV) light. The UV light contacts or impacts the phosphors to produce visible light.
When the electrons are emitted from the low voltage end, and the gaseous ions collide at the electrode 12a′ at high voltage, however, a portion of gaseous ions 16′ are sputtered on the surface 15′ of the electrode 12a′, as shown in FIG. 1B. The sputtering area of gaseous ions 16 on the electrode surface 15′ is gradually increased with long-term use. When the surface 15′ is completely covered by the gaseous ions 16, it is the end of the lifetime of the lamp.
Thus, if gaseous ion sputtering time is shorter, the lifetime of the lam is longer. That is, if the surface of the electrode is larger, and sputtering area is increased, the temperature at the end of the electrode can be reduced accordingly.
Additionally, regarding of light emission efficiency of the lamp, the larger the surface area of the electrode for emitting electrons, the more electrons are released, producing higher intensity of UV light for better light emission efficiency.
In the conventional lamp, the length L′ of the electrode is increased to increase surface area for gaseous ion sputtering. As shown in FIG. 1A, however, although the surface area is increased, the total length and weight of the hollow glass tube are increased accordingly. Due to compact size demands, the conventional lamp is unsatisfactory. Moreover, if the length is increased, effective illumination region E′ is also reduced, and thus, light emission efficiency is still insufficient.